Have a few questions regarding installing a fiberglass tub for a basement bathroom.

I am in the process of finishing my basement, and have installed a subfloor system for vapor barrier and some r value insulation. I was debating between placing the tub directly on the subfloor, or cutting out a whole in the subfloor, the exact size of the tub, and place the tub on the concrete slab. See below for my questions.

1. By putting the tub right on the concrete floor, wouldn't the tub floor that you stand on (or sit on) get cold due to being directly on the concrete? Is there some way to insulate the underside of the tub, or the tub floor?

2. Would it be wise to install the tub on the subfloor, having just a small box cut out of subfloor (matching the size of the concrete dap out) to fit the trap and drain? That way the tub is up off the concrete.

3. Do tubs ever get small micro cracks in them (the floor part that you stand on), where water can leak through these cracks from the tub floor, onto the floor below? If the tub were directly on the concrete, this water would flow onto the concrete slab, but if I had the tub on the subfloor, this water would flow onto the subfloor, eventually leading to rot, mold, etc. I had a contractor friend mention these possible micro cracks to me, so just wanted to see what would be the better way to go.

4. I read on an online post somewhere, that said when installing a tub, you should use a product like structo-lite (spelling, similar to a mortar bed for the tub) so it gets set in place, and can not move. Anyone heard of this product, or use something similar?

Any info you can provide would be great.

Thanks in advance,
Steve

oh'mike

10-11-2012 05:30 PM

I would set the tub right on the new subfloor---that way the tub will be at the correct height and not buried--

That should minimize the movement between the subfloor and the tub.

Many fiberglass tubs have a styrofoam base under it---if so then a very thin bed of masons mortar will fill the voids.
if it's hollow--a thick bed of mortar will be needed.

As to leaks? Rare----a flood under the subfloor or on top is going to cost you money---so get a good tub.